In related art, a wiring board for mounting an electronic component includes an insulating substrate made of an electric insulating material and a conductor disposed in the insulating substrate.
The wiring board which has, for example, a concave portion (castellation) disposed from a side surface to a lower surface thereof and a conductor (castellation conductor) disposed from an inner surface of the concave portion to the lower surface of the wiring board to be used as an external terminal is known (for example, refer to Patent Literature 1).